Eric Bishop wrote:> Can any give me or point me to a short and simple explanation of what HDLC
is?
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SDLC (Synchronous Data Link Control) was invented by IBM way, way back
when. It is a full-duplex, synchronous, point-to-point protocol. It is
the lowest layer in the SNA protocol suite.
A packet in SDLC begins with a flag (01111110), data bytes, a CRC byte,
and a closing flag byte. Between frames you'll see all marking bits.
Back in the 70s one could purchase a USART (Universal Synchronous
Receiver Transmitter) in a 40 pin package. Don't know about today.
I don't want to start a flame war with the Europeans, but I recall that
a European standards committee (CCITT? ISO?) decided that SDLC was
pretty cool, so they changed one bit, changed the name to HDLC
(High-level Data Link Control), and called it their own.